This invention relates to a process for preparing 5-mercapto-1,2,3-thiadiazole salts.
A 5-mercapto-1,2,3-thiadiazole salt is a chemical material having a wide application as an intermediate for pharmaceuticals, agricultural chemicals and so on, particularly as an important compound for a modifier of antibiotics.
Heretofore, as a process for preparing 5-mercapto-1,2,3-thiadiazole salt, there have been known, for example, (1) a method in which chloroacetaldehyde ethoxycarbonylhydrazone is subjected to reaction with thionyl chloride followed by the mercaptization reaction of the resulting product [Japanese Provisional Patent Publication No. 23974/1978]: ##STR1## or a method which uses a diazo compound [Tetrahedron Letters, Vol. 26, p. 2389 (1973)]: ##STR2## (2) a method in which a trihaloacetaldehyde and a hydrazine are subjected to a condensation reaction in a solvent, followed by the reaction of the resulting reaction product with a salt of a sulfide or a salt of a hydrosulfide compound [Japanese Provisional Patent Publication No. 95282/1984] or a method in which a hydrazone compound is subjected to the reaction with a sulfide compound represented by the formula: MM'S (wherein M is an alkali metal atom and M' is a hydrogen atom or an alkali metal) such as a reaction product of trichloroacetaldehyde-p-toluenesulfonylhydrazone and sodium sulfide [Japanese Provisional Patent Publication No. 51271/1984 which corresponds to European Patent application No. 103840]: ##STR3## and the like.
However, in the method of (1), there exist problems that the starting materials are unstable and hence accompanied by difficulties in handling thereof, and in the method of (2), a yield of the 5-mercapto-1,2,3-thiadiazole salt which is the intended compound is low and they were not the industrially advantageous processes.